Multi-mode charging of hierarchical anode

ABSTRACT

One aspect of the present invention provides an electrochemical cell system comprising at least one electrochemical cell configured to be connected to a power supply to recharge the cell. The electrochemical cell system comprises a plurality of electrodes and electrode bodies therein. The electrochemical cell system further comprises a switching system configured to permit modifications of the configuration of anodes and cathodes during charging of the electrochemical cell, and a controller configured to control the switching system. The controller is configured to selectively apply the electrical current to a different number of said electrode bodies based on at least one input parameter so as to adjust a rate and density of the growth of the electrodeposited metal fuel

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationSer. No. 61/414,579 filed on Nov. 17, 2010, the entirety of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a rechargeable electrochemical cellsystem.

BACKGROUND OF THE INVENTION

Electrochemical cells are well known. An electrochemical cell includesan anode or fuel electrode at which a fuel oxidation reaction takesplace, a cathode or oxidant electrode at which an oxidant reductionreaction takes place, and an ionically conductive medium for supportingthe transport of ions. In some metal-air cells, such as those disclosedin U.S. patent application Ser. No. 12/385,489 (published as U.S. PatentApplication Publication No. 2009/0284229) and Ser. No. 12/901,410(published as U.S. Patent Application Publication No. 2011/0086278),both of which are incorporated herein by reference, the fuel electrodecomprises a plurality of scaffolded electrode bodies, on which metalfuel is reduced and electrodeposited.

Electrochemical cell systems may comprise a plurality of electrochemicalcells. In some such electrochemical cell systems, the fuel electrode ofthe first cell may be coupled to a first terminal, the oxidant electrodeof each cell within the cell system may be connected to the fuelelectrode of the subsequent cell, and the oxidant electrode of the lastcell in the series may be connected to a second terminal. Thus, apotential difference is created within each individual cell, and becausethese cells are coupled in series, a cumulative potential difference isgenerated between the first and second terminals. These terminalsconnect to a load L, creating a potential difference that drivescurrent.

Among other things, the present application endeavors to provide a moreefficient and effective architecture for recharging and dischargingelectrochemical cells and electrochemical cell systems.

SUMMARY OF THE INVENTION

According to an embodiment of the present disclosure, an electrochemicalcell includes a fuel electrode comprising a series of permeableelectrode bodies arranged in spaced apart relation, an oxidant electrodespaced apart from the fuel electrode, and a charging electrode selectedfrom the group consisting of (a) the oxidant electrode, (b) a thirdelectrode spaced from the fuel electrode and the oxidant electrode, and(c) a portion of the fuel electrode. The electrochemical cell furtherincludes an ionically conductive medium contacting the electrodes, and acharge/discharge controller coupled to a plurality of the electrodebodies of the fuel electrode. The charge/discharge controller isconfigured to apply an electrical current between the charging electrodeand at least one of the permeable electrode bodies, with the chargingelectrode functioning as an anode and the at least one permeableelectrode body functioning as a cathode, such that reducible metal fuelions in the ionically conductive medium are reduced and electrodepositedas metal fuel in oxidizable form on the at least one permeable electrodebody, so that said electrodeposition causes growth of the metal fuelamong the permeable electrode bodies, with the electrodeposited metalfuel establishing an electrical connection between the permeableelectrode bodies. The charge/discharge controller is configured toselectively apply the electrical current to a different number of saidpermeable electrode bodies, each functioning as a cathode, based on atleast one input parameter so as to adjust a rate and density of thegrowth of the electrodeposited metal fuel.

According to another embodiment of the present disclosure, a method ofrecharging an electrochemical cell is provided. The electrochemical cellincludes a fuel electrode comprising a series of permeable electrodebodies arranged in spaced apart relation, an oxidant electrode spacedapart from the fuel electrode, and a charging electrode selected fromthe group consisting of (a) the oxidant electrode, (b) a third electrodespaced from the fuel electrode and the oxidant electrode, and (c) aportion of the fuel electrode. The electrochemical cell further includesan ionically conductive medium contacting the electrodes, and acharge/discharge controller coupled to a plurality of the electrodebodies of the fuel electrode. The charge/discharge controller isconfigured to apply an electrical current between the charging electrodeand at least one of the permeable electrode bodies, with the chargingelectrode functioning as an anode, and the at least one permeableelectrode body functioning as a cathode, such that reducible metal fuelions in the ionically conductive medium are reduced and electrodepositedas metal fuel in oxidizable form on the at least one permeable electrodebody, so that said electrodeposition causes growth of the metal fuelamong the permeable electrode bodies with the electrodeposited metalfuel establishing an electrical connection between the permeableelectrode bodies. The charge/discharge controller is configured toselectively apply the electrical current to a different number of saidpermeable electrode bodies based on at least one input parameter so asto adjust a rate and density of the growth of the electrodeposited metalfuel.

The method includes selecting, based on the at least one inputparameter, between a higher density progressive growth mode and a higherrate growth mode. The method further includes charging theelectrochemical cell based on the selected one of the higher densityprogressive charge mode and the higher rate growth mode. In the higherdensity progressive growth mode, said charging comprises applying theelectrical current to a terminal one of the permeable electrode bodies,with the charging electrode functioning as the anode and the terminalelectrode body functioning as the cathode, such that the reducible metalfuel ions are reduced and electrodeposited as metal fuel in oxidizableform on the terminal permeable electrode body. The electrodepositioncauses growth of the metal fuel among the permeable electrode bodiessuch that the electrodeposited metal fuel establishes an electricalconnection between the terminal electrode body and each subsequentpermeable electrode body with said reduction and deposition occurring oneach subsequent permeable electrode body upon establishment of saidelectrical connection. In the higher rate growth mode, said chargingcomprises applying the electrical current simultaneously to a pluralityof said electrode bodies, with the charging electrode functioning as theanode and each of the plurality of electrode bodies functioning ascathodes, such that the reducible metal fuel ions are reduced andelectrodeposited as metal fuel in oxidizable form on the terminalpermeable electrode body, said electrodeposition causing growth of themetal fuel among the permeable electrode bodies. The method furtherincludes disconnecting the electrical current to discontinue thecharging.

Other objects, features, and advantages of the present invention willbecome apparent from the following detailed description, theaccompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of an electrochemical cellsystem that includes two electrochemical cells;

FIG. 2 illustrates an exploded view of the electrochemical cell systemof FIG. 1;

FIG. 3 illustrates an electrode holder of one of the electrochemicalcells of FIG. 1;

FIG. 4 illustrates the electrode holder of FIG. 3, holding a fuelelectrode and a plurality of spacers connected to the electrode holder

FIG. 5 illustrates one of the spacers of FIG. 4 in greater detail;

FIG. 6 illustrates a connection between the spacers of FIG. 5 and theelectrode holder of FIG. 3 in greater detail;

FIG. 7 schematically illustrates electrical connections between theelectrochemical cell and an external load or power supply according toan embodiment of a cell system in accordance with the present invention;

FIG. 8 schematically illustrates electrical connections between theelectrochemical cell and an external load or power supply according toan embodiment of a cell system in accordance with the present invention;

FIG. 9 schematically illustrates a switching system according to anembodiment of the cell system of FIG. 8;

FIG. 10 schematically illustrates a switching system according toanother embodiment of the cell system of FIG. 8;

FIG. 11 schematically illustrates a switching system according toanother embodiment of the cell system of FIG. 8;

FIGS. 12A-C schematically illustrate the embodiments of FIGS. 9-11further comprising a plurality of cells a switching system according toanother embodiment of the cell of FIG. 8;

FIG. 13 schematically illustrates a switching system similar to theembodiment of FIG. 11, further comprising a controller;

FIG. 14 shows a flowchart illustrating an embodiment of a method ofcharging the cell, in accordance with the present invention;

FIG. 15 shows a flowchart illustrating an embodiment of a method ofdischarging the cell;

FIG. 16 schematically illustrates a switching system according toanother embodiment of the cell of FIG. 8; and,

FIG. 17 shows a flowchart illustrating an embodiment of an algorithm forcharging the cell, in accordance with the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS OF THE INVENTION

FIGS. 1 and 2 illustrate an electrochemical cell system 100 thatincludes two electrochemical cells 10 according to an embodiment of theinvention. As illustrated, each cell 10 includes a fuel electrode 12,and an oxidant electrode 14 that is spaced from the fuel electrode 12.The fuel electrode 12 supported by an electrode holder 16. Theelectrochemical system 100 also includes a cover 19 that is used tocover the electrochemical cells 10 on one side of the system 100, whileone of the electrode holders 16 is used to cover the opposite side ofthe system 100, as illustrated in FIG. 1.

In an embodiment, the fuel electrode 12 is a metal fuel electrode thatfunctions as an anode when the cell 10 operates in discharge, orelectricity generating, mode, as discussed in further detail below. Inan embodiment, the fuel electrode 12 may comprise a plurality ofpermeable electrode bodies 12 a-d, such as screens that are made of anyformation able to capture and retain, through electrodepositing, orotherwise, particles or ions of metal fuel from an ionically conductivemedium that circulates in the cell 10, as discussed in further detailbelow. Components of the cell 10, including for example, the fuelelectrode 12, the permeable electrode bodies 12 a-d thereof, and theoxidant electrode 14, may be of any suitable construction orconfiguration, including but not limited to being constructed of Nickelor Nickel alloys (including Nickel-Cobalt, Nickel-Iron, Nickel-Copper(i.e. Monel), or superalloys), Copper or Copper alloys, brass, bronze,or any other suitable metal. In an embodiment, a catalyst film may beapplied to some or all of the permeable electrode bodies 12 a-d and/orthe oxidant electrode 14, and have a high surface material that may bemade of some of the materials described above. In an embodiment, thecatalyst film may be formed by techniques such as thermal spray, plasmaspray, electrodeposition, or any other particle coating method.

The fuel may be a metal, such as iron, zinc, aluminum, magnesium, orlithium. By metal, this term is meant to encompass all elements regardedas metals on the periodic table, including but not limited to alkalimetals, alkaline earth metals, lanthanides, actinides, and transitionmetals, either in atomic, molecular (including metal hydrides), or alloyform when collected on the electrode body. However, the presentinvention is not intended to be limited to any specific fuel, and othersmay be used. The fuel may be provided to the cell 10 as particlessuspended in the ionically conductive medium. In some embodiments, ametal hydride fuel may be utilized in cell 10.

The ionically conductive medium may be an aqueous solution. Examples ofsuitable mediums include aqueous solutions comprising sulfuric acid,phosphoric acid, triflic acid, nitric acid, potassium hydroxide, sodiumhydroxide, sodium chloride, potassium nitrate, or lithium chloride. Themedium may also use a non-aqueous solvent or an ionic liquid. In thenon-limiting embodiment described herein, the medium is aqueouspotassium hydroxide. In an embodiment, the ionically conductive mediummay comprise an electrolyte. For example, a conventional liquid orsemi-solid electrolyte solution may be used, or a room temperature ionicliquid may be used, as mentioned in U.S. patent application Ser. No.12/776,962 (published as U.S. Patent Application Publication No.2010/0285375), the entirety of which is incorporated herein. In anembodiment where the electrolyte is semi-solid, porous solid stateelectrolyte films (i.e. in a loose structure) may be utilized.

The fuel may be oxidized at the fuel electrode 12 when the fuelelectrode 12 is operating as an anode, and an oxidizer, such as oxygen,may be reduced at the oxidant electrode 14 when the oxidant electrode 14is operating as a cathode, which is when the cell 10 is connected to aload L and the cell 10 is in discharge or electricity generation mode,as discussed in further detail below. The reactions that occur duringdischarge mode may generate by-product precipitates, e.g., a reduciblefuel species, in the ionically conductive medium. For example, inembodiments where the fuel is zinc, zinc oxide may be generated as aby-product precipitate/reducible fuel species. The oxidized zinc orother metal may also be supported by, oxidized with or solvated in theelectrolyte solution, without forming a precipitate (e.g. zincate may bea dissolved reducible fuel species remaining in the fuel). During arecharge mode, which is discussed in further detail below, the reduciblefuel species, e.g., zinc oxide, may be reversibly reduced and depositedas the fuel, e.g., zinc, onto at least a portion of the fuel electrode12 that functions as a cathode during recharge mode. During rechargemode, either the oxidant electrode 14 or a separate charging electrode70 (which may be of similar construction or configuration as permeableelectrode bodies 12 a-d in some embodiments), and/or another portion ofthe fuel electrode 12, as described below, functions as the anode. Theswitching between discharge and recharge modes is discussed in furtherdetail below.

The electrode holder 16 defines a cavity 18 in which the fuel electrode12 is held. The electrode holder 16 also defines an inlet 20 and anoutlet 22 for the cell 10. The inlet 20 is configured to allow theionically conductive medium to enter the cell 10 and/or recirculatethrough the cell 10. The inlet 20 may be connected to the cavity 18 viaan inlet channel 24, and the outlet 22 may be connected to the cavity 18via an outlet channel 26. As illustrated in FIG. 3, the inlet channel 24and the outlet channel 26 may each provide a meandering tortuous paththrough which the ionically conductive medium may flow. The meanderingpath defined by the inlet channel 24 preferably does not include anysharp corners in which the flow of the medium may become stagnated or inwhich any particulates in the medium may collect. As discussed infurther detail below, the length of the channels 24, 26 may be designedto provide an increased ionic resistance between cells that are fluidlyconnected in series.

For each cell 10, a permeable seal member 17 may be bonded betweensealing surfaces on the electrode holders 16 and/or the cover 19, asappropriate, to enclose at least the fuel electrode 12 in the cavity 18.The seal member 17 also covers the inlet and outlet channels 24, 26. Theseal member 17 is non-conductive and electrochemically inert, and ispreferably designed to be permeable to the ionically conductive mediumin the orthogonal direction (i.e., through its thickness), withoutpermitting lateral transport of the ionically conductive medium. Thisenables the ionically conductive medium to permeate through the sealmember 17 for enabling ion conductivity with the oxidant electrode 14 onthe opposing side to support the electrochemical reactions, without“wicking” the ionically conductive medium laterally outwardly from thecell 10. A few non-limiting examples of a suitable material for the sealmember 17 are EPDM and TEFLON®.

In the illustrated embodiment, the cavity 18 has a generallyrectangular, or square, cross-section that substantially matches theshape of the fuel electrode 12. The cavity 18 may be connected to theinlet channel 24 by a plurality of inlets 34 so that when the ionicallyconductive medium and precipitates or reducible fuel species enter thecavity 18, the ionically conductive medium and fuel are distributedalong a side of the fuel electrode 12. In some embodiments, one side ofthe cavity 18, specifically, the side of the cavity 18 that is connectedto the inlet channel 24, may include a plurality of fluidization zones,such as is described in U.S. patent application Ser. No. 12/901,410,incorporated herein in its entirety by reference. In other embodiments,the ionically conductive medium may enter the cavity 18 through adiffuser, such as is described in U.S. Provisional Patent ApplicationNo. 61/301,377, now converted into U.S. patent application Ser. No.13/019,923 (published as U.S. Patent Application Publication No.2011/0189551), each of which is also incorporated herein in its entiretyby reference. In various embodiments, the ionically conductive mediummay flow in parallel or in series through a plurality of cells 10. Insome embodiments, the ionically conductive medium may utilize acombination of parallel and series flows. Furthermore, in variousembodiments the ionically conductive medium may flow at a varying rate,and even may flow intermittently (i.e. static for a time) duringoperation of the one or more cells 10.

As illustrated in FIG. 4, a plurality of spacers 40, each of whichextends across the fuel electrode 12 in a spaced relation to each other,may be connected to the electrode holder 16 so that the fuel electrode12 may be held in place relative to the electrode holder 16 and to theoxidant electrode 14. In an embodiment, the plurality of permeableelectrode bodies 12 a-12 d, as illustrated in FIG. 2, may be separatedby sets of the plurality of spacers 40, so that each set of spacers 40is positioned in between adjacent electrode bodies to electricallyisolate the electrode bodies 12 a-12 d from each other. Within each setof spacers 40 between adjacent electrode bodies, the spacers 40 arepositioned in a spaced relation in a manner that creates so-called “flowlanes” 42 therebetween, as discussed in greater detail below. The flowlanes 42 are three-dimensional and have a height that is substantiallyequal to the height of the spacers 40. In an embodiment, the spacers 40may be provided by a single frame that has cut-outs corresponding to theflow lanes. In an embodiment, the flow lanes 42 may include a foam orhoneycomb-type structure that is configured to allow the ionicallyconductive medium to flow therethrough. In an embodiment, the flow lanes42 may include an array of pins that are configured to disrupt the flowof the ionically conductive medium through the flow lanes. In anembodiment, the frame, spacers 40, flow lanes 42, and/or other elementsof cell 10 may be defined by plastic formed by injection molding, orepoxy/insulating material formed using chemical processes. Theillustrated embodiment is not intended to by limiting in any way.

The spacers 40 are non-conductive and electrochemically inert so theyare inactive with regard to the electrochemical reactions in the cell10. The spacers 40 are preferably sized so that when they are connectedto the electrode holder 16, the spacers 40 are in tension, which allowsthe spacers 40 to press against the fuel electrode 12, or one of theelectrode bodies 12 a-12 c, so as to hold the fuel electrode 12 orbodies thereof in a flat relation relative to the electrode holder 16.The spacers 40 may be made from a plastic material, such aspolypropylene, polyethylene, noryl, fluoropolymer, etc. that allows thespacers 40 to be connected to the electrode holder 16 in tension. Invarious embodiments, the spacers 40 may be attached together bytechniques such as (but not limited to) thermal bonding, chemicalbonding, or ultrasonic welding/bonding

In the embodiment illustrated in FIG. 5, each spacer has an elongatedmiddle portion 44, and a shaped connecting portion 46 at each end. Theshaped connecting portions 46 are configured to be held by openings 48having substantially similar shapes in the electrode holder 16, asillustrated in FIG. 6. In the illustrated embodiment, the shapedportions 46 and the openings 48 have a substantially triangular shape,although the illustrated shape is not intended to be limiting in anyway. The substantially triangular shape provides surfaces 50 on oppositesides of the elongated portion 44 of the spacer 40 that are configuredto contact corresponding surfaces 52 on the electrode holder 16. Becausethe surfaces 50, 52 are angled with respect to a major axis MA of theelongated portion 44 of the spacer 40 and the tension in the spacer 40will be along the major axis MA, the forces created by the tension maybe distributed across a larger surface, as compared to a shaped portionhaving a circular or square shape with the same area.

Once the spacers 40 have been connected to the electrode holder 16 viathe end portions 46, the flow lanes 42 are defined across the cavity 18of the electrode holder 16. The spacers 40 are configured to essentiallyseal off one flow lane 42 a from an adjacent flow lane 42 b, that isseparated by one of the spacers 40 so that the ionically conductivemedium is guided to generally flow in substantially one direction.Specifically, the ionically conductive medium may generally flow in afirst direction FD across the fuel electrode 12, from the inlet channel24 to the outlet channel 26. A suitable pressure drop is generatedbetween the inlet channel 24 and the inlets 34 so that the ionicallyconductive medium may flow across the cavity 18 and to the outletchannel 26, even when the cell 10 is oriented such that the flow issubstantially upward and against gravity. In an embodiment, theionically conductive medium may also permeate through the fuel electrode12, or an individual permeable electrode body 12 a-12 d, in a seconddirection SD and into a flow lane that is on the opposite side of thefuel electrode 12 or permeable electrode body 12 a-12 d.

As illustrated in the embodiment of FIG. 7, the fuel electrode 12 ofcell 10 in electrochemical cell system 100 may be selectively connectedto an external load L so that electrons given off by the fuel as thefuel is oxidized at the fuel electrode 12 may flow to the external loadL. A switching system 60 comprising a plurality of switches, mayselectively electrically connect each of the individual permeableelectrode bodies 12 a-12 d of the fuel electrode 12, and may alsoselectively connect the permeable electrode bodies 12 a-12 d to theoxidant electrode 14. As shown, in some embodiments electrochemical cellsystem 100 may further comprise other cells 10. In an embodiment, theswitching system 60 may comprise a terminal selector system 62configured to couple or decouple the external load L for use indischarging the cell 10, or couple or decouple a power supply PS for usein charging the cell 10. In another embodiment the switching system 60and the terminal selector system 62 may be separate, but may, in anembodiment, communicate with each other. The switching system 60 isdiscussed in greater detail below.

The oxidant electrode 14 functions as a cathode when the oxidantelectrode 14 is connected to the external load L and the cell 10operates in discharge mode. When functioning as a cathode, the oxidantelectrode 14 is configured to receive electrons from the external load Land reduce an oxidizer that contacts the oxidant electrode 14. Theoxidizer may be any species of the oxidant available for oxidation atthe charging electrode. For example, the species may be a free ion, oran ion bonded to or coordinated with other ions or constituents in theionically conductive medium. In an embodiment, the oxidant electrode 14comprises an air breathing electrode and the oxidizer comprises oxygenin the surrounding air.

The oxidizer may be delivered to the oxidant electrode 14 by a passivetransport system. For example, where oxygen present in ambient air isthe oxidizer, simply exposing the oxidant electrode 14 to ambient airvia openings in the cell, such as the openings that are provided bygrooves 54 in the cover 19 and grooves 56 in the electrode holder 16provided in the center of the electrochemical cell system 100, may besufficient to allow diffusion/permeation of oxygen into the oxidantelectrode 14. Other suitable oxidizers may be used and embodimentsdescribed herein are not limited to the use of oxygen as the oxidizer. Aperipheral gasket 15 may be positioned between the periphery of theoxidant electrode 14 and the cover 19 or electrode holder 16, asappropriate, to prevent the ionically conductive medium from leakingaround the oxidant electrode 14 and into the area in the grooves 54, 56for air exposure.

In other embodiments, a pump, such as an air blower, may be used todeliver the oxidizer to the oxidant electrode 14 under pressure. Theoxidizer source may be a contained source of oxidizer. In an embodiment,the oxygen may be recycled from the cell 10, such as is disclosed inU.S. patent application Ser. No. 12/549,617 (published as U.S. PatentApplication Publication No. 2010/0119895), incorporated in its entiretyherein by reference. Likewise, when the oxidizer is oxygen from ambientair, the oxidizer source may be broadly regarded as the deliverymechanism, whether it be passive or active (e.g., pumps, blowers, etc.),by which the air is permitted to flow to the oxidant electrode 14. Thus,the term “oxidizer source” is intended to encompass both containedoxidizers and/or arrangements for passively or actively deliveringoxygen from ambient air to the oxidant electrode 14.

Electricity that can be drawn by the external load L is generated whenthe oxidizer at the oxidant electrode 14 is reduced, while the fuel atthe fuel electrode 12 is oxidized to an oxidized form. The electricalpotential of the cell 10 is depleted once the fuel at the fuel electrode12 is entirely oxidized or oxidation is arrested due to passivation ofthe fuel electrode. A portion of the switching system 60 may bepositioned in between the oxidant electrode 14 and the load L so thatthe oxidant electrode 14 may be connected and disconnected from the loadL, as desired. Again, more details about the switching system 60, andthe electrical configuration thereof, is provided below.

To limit or suppress hydrogen evolution at the fuel electrode 12 duringdischarge mode and during quiescent (open circuit) periods of time,salts may be added to retard such a reaction. Salts of stannous, lead,copper, mercury, indium, bismuth, or any other material having a highhydrogen overpotential may be used. In addition, salts of tartrate,phosphate, citrate, succinate, ammonium or other hydrogen evolutionsuppressing additives may be added. In an embodiment, metal fuel alloys,such as Al/Mg may be used to suppress hydrogen evolution. Otheradditives may also or alternatively be added to the ionically conductivemedium, including, but not limited to additives which enhance theelectrodeposition process of the metal fuel on the fuel electrode 12,such as is described in U.S. Provisional Patent Application 61/304,928,now converted into U.S. patent application Ser. No. 13/028,496,incorporated in its entirety herein by reference. After the fuel in thecell 10 has been entirely oxidized, or whenever it is desirable toregenerate the fuel within the cell 10 by reducing oxidized fuel ionsback to fuel, the fuel electrode 12 and the oxidant electrode 14 may bedecoupled from the external load L and coupled to a power supply PS. Asnoted above, such connections may be made, for example, with the use ofthe switching system 60 and the terminal selector system 62.

The power supply PS is configured to charge the cell 10 by applying apotential difference between the fuel electrode 12 and the oxidantelectrode 14 such that the reducible species of the fuel is reduced andelectrodeposited onto at least one of the permeable electrode bodies 12a-12 d and the corresponding oxidation reaction takes place at theoxidant electrode 14, which is typically oxidation of an oxidizablespecies to evolve oxygen, which may be off-gassed from the cell 10. Inan embodiment wherein oxygen is the oxidant, oxygen ions in an aqueouselectrolytic solution are oxidized. The oxygen ions may be availablefrom an oxide of the fuel (e.g., ZnO when zinc is the fuel), hydroxideions (OH⁻), or water molecules (H₂O). As described in detail in U.S.patent application Ser. No. 12/385,489, which has been incorporatedherein by reference, in an embodiment only one of the permeableelectrode bodies, such as 12 a, is connected to the power supply PS sothat the fuel reduces onto the permeable electrode body andprogressively grows to and on the other permeable electrode bodies 12b-12 d, one by one. The switching system 60 may control how thepermeable electrode bodies 12 a-12 d and the oxidant electrode 14participate in the electrochemical reactions of the cell, as isdescribed in greater detail below.

FIG. 8 shows an embodiment where a separate charging electrode 70 ofcell 10 in electrochemical cell system 100 is provided to function asthe charging electrode, rather than the oxidant electrode 14. Again, insome embodiments other cells 10 may be part of electrochemical cellsystem 100, as shown. As illustrated in FIG. 2, the separate chargingelectrode 70 may be positioned between the fuel electrode 12 and theoxidant electrode 14, with a spacer 72 and the seal member 17 beingpositioned between the separate charging electrode 70 and the oxidantelectrode 14. The spacer 72 is non-conductive and has openings throughwhich the ionically conductive medium may flow.

In the embodiment described above with respect to FIG. 7, the oxidantelectrode 14 functions as the cathode during power generation/discharge,and as the anode during charging, as described above. In FIG. 8, theoxidant electrode 14 remains the cathode during powergeneration/discharge, but may be disconnected during charging, while theseparate charging electrode 70 is connected to the power supply PS tofunction as the anode. During current generation, the fuel on the fuelelectrode 12 is oxidized, generating electrons that are conducted topower the load L and then conducted to the oxidant electrode 14 forreduction of the oxidizer (as discussed in more detail above). Inembodiments comprising the separate charging electrode 70, the switchingsystem 60 may control how the permeable electrode bodies 12 a-12 d theoxidant electrode 14, and the separate charging electrode 70 participatein the electrochemical reactions of the cell, as is described in greaterdetail below.

It is also possible in any of the embodiments of the invention to applythe cathodic potential to any or all of the electrode bodies 12 a-12 dof the fuel electrode 12, rather than to just one to producebody-by-body progressive growth. Progressive growth emanating from oneterminal is advantageous because it provides more density of theelectrodeposited fuel. Specifically, the growth in the previouslyconnected electrode bodies continues as each subsequent body isconnected by the progressing growth. This and other advantages arediscussed in greater detail in U.S. patent application Ser. No.12/385,489, which has been incorporated herein by reference. With allthe electrode bodies subject to the same potential, the growth will onlyoccur until a short occurs between the charging electrode, which is theoxidant electrode 14 in the embodiment of FIG. 7 and the separatecharging electrode 70 in the embodiment of FIG. 8, and the electrodebody proximate to it. Thus, it is possible to have a faster, but lessdense, growth in this manner, which may be amenable to certainre-charging needs.

The embodiments illustrated in FIGS. 7 and 8 should not be considered tobe limiting in any way and are provided as non-limiting examples of howthe cell 10 may be configured to be rechargeable. The recharge mode ofthe present invention, in the context of the switching system 60, isdiscussed in greater detail below. As another example, U.S. patentapplication Ser. No. 12/885,268 (published as U.S. Patent ApplicationPublication No. 2011/0070506), filed on Sep. 17, 2010, the entirecontent of each of which is incorporated herein by reference, describesembodiments of a rechargeable electrochemical cell system withcharge/discharge mode switching in the cells.

Returning to FIG. 4, after the ionically conductive medium has passedthrough the fuel electrode 12, the medium may flow into the outletchannel 26 that is connected to the outlets 36 of the cavity 18 of theelectrode holder 16 and the outlet 22. The outlet 22 may be connected tothe inlet 20 in embodiments where the medium is recirculated in the cell10, or to an inlet of an adjacent cell, as discussed in further detailbelow, when a plurality of cells 10 are fluidly connected in series. Inan embodiment, the outlet 22 may be connected to a vessel to collect themedium that has been used in the cell 10. Again, in various embodimentsthe flow of the ionically conductive medium may vary, for example byflowing through a plurality of cells 10 in series or parallel, at aconstant rate or a varying rate, continuously or intermittently.

The cells 10 illustrated in FIGS. 1 and 2 may be fluidly connected inseries. Details of embodiments of cells that are connected in series areprovided in U.S. patent application Ser. No. 12/631,484 (published asU.S. Patent Application Publication No. 2010/0316935), filed Dec. 4,2009 and incorporated herein by reference in its entirety. The outlet 22of a first cell 10 may be fluidly connected to the inlet 20 of a secondcell 10, and the outlet 22 of the second cell 10 may be connected to theinlet 20 of a third cell, and so on. Although the embodiment of FIGS. 1and 2 illustrates two cells 10, additional cells may be stacked andfluidly connected to the illustrated cells. Due to the meandering,tortuous paths that are created by the inlet channel 24 and the outletchannel 26, described above and illustrated in FIGS. 3 and 4, the lengthof the flow passageways for the medium via the channels 24, 26 isgreater than the distance between the fuel electrode 12 and the oxidantelectrode 14 in each of the cells 10. This creates an ionic resistancebetween the pair of fluidly connected cells that is greater than anionic resistance within an individual cell 10. This may reduce orminimize internal ionic resistance loss of the stack of cells 100, asdiscussed in U.S. patent application Ser. No. 12/631,484.

In an embodiment of operation, the fuel electrode 12, which already hasmetal fuel deposited thereon, is connected to the load L and the oxidantelectrode 14 is connected to the load L. The ionically conductive mediumenters the inlet 20 under positive pressure and flows through the inletchannel 24, the inlets 34 of the cavity 18, and into the flow lanes 42.The ionically conductive medium flows across the permeable electrodebodies 12 a-12 d in the flow lanes 42 defined by the elongated middleportions 22 of the spacers 40. The ionically conductive medium may alsopermeate through the permeable electrode bodies 12 a-12 d of the fuelelectrode 12. The ionically conductive medium simultaneously contactsthe fuel electrode 12 and the oxidant electrode 14, thereby allowing thefuel to oxidize and conduct electrons to the load L, while the oxidizeris reduced at the oxidant electrode 14 via the electrons that areconducted to the oxidant electrode 14 by the load L. After the ionicallyconductive medium has passed through the flow lanes 42, the medium flowsout of the cavity 18 via the outlets 36 of the cavity 18, through theoutlet channel 24, and out the outlet 22 of the cell 10.

When the potential of the cell 10 has been depleted or when it isotherwise desirable to recharge the cell 10, the fuel electrode 12 isconnected to the negative terminal of the power supply PS and thecharging electrode, which may be the oxidant electrode 14 or theseparate charging electrode 70, is connected to the positive terminal ofthe power supply PS. Such connections may again be through the switchingsystem 60, discussed below. In the charging or recharge mode, a cathodeportion of the fuel electrode 12 becomes the cathode and an anodeportion of the fuel electrode 12 and/or the charging electrode 14, 70becomes the anode, as is described in greater detail below. By providingelectrons to a cathode portion of the fuel electrode 12, fuel ions mayreduce into fuel and redeposit onto the permeable electrode bodies 12a-12 d, as is described in greater detail below, while the ionicallyconductive medium circulates through the cell 10 in the same manner asdescribed above with respect to the discharge mode.

The flow lanes 42 provide directionality and distribution of theionically conductive medium across the fuel electrode 12. The flow lanes42 may also prevent the particulates from settling and/or covering theelectrodes. When the cell 10 is in charging mode, the improveddistribution of the particulates across the fuel electrode 12 allows fora more uniform deposition of the reduced fuel onto the fuel electrode12, which improves the density of the fuel on the fuel electrode 12, andincreases the capacity and energy density of the cell 10, therebyenhancing the cycle-life of the cell 10. In addition, by having theability to control the distribution of the precipitates or reactionby-product during discharge, early passivation/deposition of theby-product on the fuel electrode 12 may be prevented. Passivation leadsto lower fuel utilization and lower cycle life, which is undesirable.

The examples of FIGS. 1-8 are not limiting, and are provided solely forcontext to understand general principles of an embodiment of the cells10 of the cell system 100. Any cell construction or configuration may beused. With an understanding of the cell system provided, attention isturned to the configuration and operation of the switching system 60 ofthe invention.

As noted, during a charging mode for the cell 10, a potential differenceis applied across electrodes in the cell 10. Although either the oxidantelectrode 14 or the separate charging electrode 70 generally function asthe anode during charging, an anodic potential may be applied to otherelectrodes, such as some of the electrode bodies in the fuel electrode12. Likewise, during charging a cathodic potential may be initiallyapplied to electrode body 12 a of the fuel electrode 12, but may also beinitially applied to one or more of the other permeable electrode bodies12 b-12 d of the fuel electrode 12. As such, those permeable electrodebodies 12 a-12 d of fuel electrode 12 having a cathodic potential behaveas a cathode during charge, and serve as a reduction site for areducible fuel species, such as the oxidized fuel ions created in thecell during discharging.

As the reducible fuel species is reduced on those of permeable electrodebodies 12 a-12 d having the cathodic potential, the oxidant electrode 14or the separate charging electrode 70 and/or those of the permeableelectrode bodies 12 b-12 d having the anodic potential will oxidize anoxidizable oxygen species, such as the reduced oxidant species createdin the cell during discharging. Thus, when the cell 10 is a metal-aircell, the reducible metal fuel species is being reduced andelectrodeposited on some of the permeable electrode bodies 12 a-12 d ofthe fuel electrode 12, and the oxidizable oxygen species is beingoxidized to oxygen gas, which may be off-gassed from the cell 10. Inthis embodiment, those electrodes and electrode bodies having an anodicpotential may be considered an oxygen evolving electrode (OEE).

To determine which of the electrodes (i.e. permeable electrode bodies 12a-d, the oxidant electrode 14 and/or the separate charging electrode 70)have anodic potentials or cathodic potentials during charging,electrical connections therebetween may be controlled by the switchingsystem 60, as is discussed in greater detail below.

It may be advantageous to the fuel growth for the potential differenceused to charge the cell 10 to be applied between adjacent bodies in thecell 10, such that an electrode body having the anodic potential isadjacent to an electrode body having the cathodic potential. Oncesufficient fuel growth has occurred on the electrode body having thecathodic potential, the electrode having the anodic potential maychange, so that the permeable electrode body that previously was part ofa set of electrode bodies having an anodic potential may become part ofa set of electrode bodies having the cathodic potential. In anembodiment wherein there are N permeable electrode bodies, theapplication of the anodic potential from the power source to permeableelectrode bodies 2 to N and the charging electrode may compriseconnecting all of the electrode bodies plus the charging electrodetogether at the same time, then disconnecting each of electrode bodies 2to N in order. Alternatively, in an embodiment, the application of theanodic potential from the power source to permeable electrode bodies 2to N and the charging electrode could comprise connecting anddisconnecting each of the electrode bodies and the charging electrodeindividually in order (such that electrode body 2 is connecting to theanodic potential, then is disconnected and electrode 3 is connected tothe anodic potential, and so on until the charging electrode is finallyconnected to complete the growth).

In an embodiment, the charging electrode may merely be the lastelectrode to receive the anodic potential during charging. For example,the charging electrode could be the oxidant electrode or a separateelectrode. When the charging electrode is a separate electrode, it couldhave a specialized construction different from the electrode bodies ofthe fuel electrode, or could be the same as the permeable electrodebodies (i.e. just one more electrode body), but for the fact that growthof the fuel during charging does not continue past it.

In the above-described embodiment illustrated in FIGS. 1-2, theprogressive changing of which electrode(s) have the anodic potential mayfollow the fuel growth through each of the permeable electrode bodies 12a-12 d, so that an electrode having an anodic potential remains theelectrode body spaced adjacent to an electrode having the cathodicpotential. As shown in the embodiments of the following Figures, theswitch system 60 may be configured to selectively connect and disconnectthe various electrodes and electrode bodies to maintain the adjacentpositions of the anodic potential and the cathodic potential.

FIGS. 9-12 show embodiments of the switching system 60 of the cell 10.The cell 10 is connectable to the power supply PS, the load L, or toother cells 10 in series, through a first terminal 130 and a secondterminal 140, wherein the first terminal 130 is negative (cathodic)during recharging, and the second terminal 140 is positive (anodic)during recharging. As shown, the cell 10 has a fuel electrode 12comprising permeable electrode bodies 12 a-12 d, a charging electrode70, and an oxidant electrode 14. In an embodiment, the plurality ofswitches may selectively couple at least some of the permeable electrodebodies 12 b-12 d to a power source, such as power supply PS, forapplication of an anodic potential during a recharging mode of the cell10, in which a cathodic potential is applied to at least electrode body12 a, as will be described in greater detail below.

In FIG. 9, the switching system 60 includes a bypass switch 150,configured to provide a direct connection between the first terminal 130and the second terminal 140. The bypass switch 150 may be similar tothat described in U.S. patent application Ser. No. 12/885,268, which hasbeen incorporated herein in its entirety by reference. A cell 10 can bebypassed with bypass switch 150 for a number of reasons that affect theperformance of the stack.

For example, a short between charging electrode 70 and the electrodebodies 12 a-12 d having a cathodic potential during charge (detected byvoltage measurement as described below) may lead to expense of parasiticpower during charge. An electrical short may lead to a sudden drop involtage between the charging and fuel electrodes as the current isshunted between the charging and fuel electrodes. Another example isduring discharge, where any cell 10 that has a higher kinetic or ohmicloss affects the round trip efficiency and discharge power of the stack.Also, consumption of fuel in the cell 10 during discharge earlier thanother cells 10 can lead to voltage reversal in the cell 10 and stackpower loss, and can be prevented by bypassing the cell 10 when thedischarge voltage falls below a critical value. Complete consumption ofzinc or other fuel during discharge leads to a sudden drop in voltagebetween the fuel and oxidant electrodes. Any other criteria to detectthe performance of cells 10 may be used, and the examples herein are notlimiting. Certain cells 10 may not meet performance requirements (forexample, maximum power during discharge) due to yield issues andproblems related to fabrication and assembly of electrodes. These cells10 can be permanently placed in bypass mode. Other cells 10 may meetperformance requirements initially, however may have cycle life issuesand can be placed in bypass mode after the performance falls below arequired limit. Thus, bypassing a cell 10 through bypass switch 150provides an option to increase reliability and performance of the stack.

The switching system 60 of FIG. 9 also includes an oxidant electrodeswitch 160 associated with the oxidant electrode 14. The oxidantelectrode switch 160 would be closed during discharge, so that anelectric potential across the fuel electrode 12 and the oxidantelectrode 14 may allow a current to be drawn by a load L connectedbetween the first terminal 130 and the second terminal 140, which duringdischarge would have positive and negative polarities respectively.

A charging electrode switch 170 may be associated with the chargingelectrode 70, such that the charging electrode 70 may be electricallyconnected to the second terminal 140 when the power supply PS isconnected between the first terminal 130 and the second terminal 140. Asdiscussed below, the charging electrode 70 may not always have an anodicpotential applied to it, and in an embodiment may only have an anodicpotential when fuel growth between it and electrode body 12 d isdesired. Also shown are switches 180, 190, and 200, associated withelectrode bodies 12 b-12 d respectively, all of which are configured toconnect electrode bodies 12 b-12 d to the second terminal 140 as well.

As was noted, it is advantageous that an electrode having an anodicpotential be adjacent to an electrode having a cathodic potential, sothat growth on the electrode having the cathodic potential is enhanced.Such enhancement may, for example, include greater density of fuelgrowth than if the electrode having the anodic potential is further fromthe closest electrode having the cathodic potential (i.e. if a neutralelectrode separates the electrodes having the anodic and cathodicpotentials). This enhanced density may be due to the initial dendritesthat first contact the anodic body being disrupted because they lacksufficient cross-section to carry the current between the anodic andcathodic bodies. That is, they burn off similarly to a fuse elementsubject to excess current. This delays shorting between the anodic andcathodic bodies, which takes place when the density has increasedfurther to provide dendrites of sufficient cross-sectional area(individually and/or collectively) to enable the current conductionwithout disruption. Another advantage may be lower electrolyte IR lossin configurations where the distance between the charging electrode 70and the fuel electrode 12 is lower, as compared to configurationswherein the electrode having the anodic potential is further from theclosest electrode having the cathodic potential (i.e. where neutralelectrodes separate the electrodes having the anodic and cathodicpotentials). This IR efficiency advantage resulting from less distancebetween anodic and cathodic electrodes may be realized both inembodiments where metallic growth is occurring between the electrodesand in other embodiments, such as a metal hydride fuel where thehydrogen ions are being reduced.

To achieve progressive modification of which electrodes have the anodicpotential, to account for shifts between electrodes having an anodicpotential versus electrodes having a cathodic potential, the cell 10 inthe charging mode would be configured such that the bypass switch 150 isopen, so that current does not bypass the cell 10. Because the cell isin a charging mode, the oxidant electrode switch 160 is also open, sothat the oxidant electrode 14 is electrically disconnected from the cell10. Since initially fuel growth is desired on electrode body 12 a, onlyelectrode body 12 a is electrically connected to first terminal 130,applying the cathodic potential thereto. To establish an anodicpotential on the electrode body adjacent to electrode body 12 a, atleast electrode body 12 b will be electrically connected to secondterminal 140. To achieve this electrical connection in the illustratedembodiment, at least switch 180 is closed. In an embodiment, electrodebodies 12 c-12 d, and charging electrode 70 may also be electricallyconnected to second terminal 140, and thus may also have the anodicpotential. Because of the potential difference between the electrode(s)having the anodic potential (i.e. initially electrode body 12 a) and theelectrode(s) having the cathodic potential (i.e. initially at leastelectrode body 12 b), reducible fuel species in the ionically conductivemedium may be reduced at the electrode having the initial cathodicpotential (electrode body 12 a) while cations in the ionicallyconductive medium are oxidized at electrode body 12 b (and any otherbody/electrode to which the anodic potential is applied).

Once fuel growth on the electrodes having the cathodic potentialprogresses to a certain point, for example, to the point where anelectrical connection is formed between the electrode(s) having thecathodic potential and the electrode(s) having the anodic potential, theswitching system 60 may disconnect the shorting electrode body that hadthe anodic potential, such that that electrode body has a cathodicpotential applied to it, and a potential difference may be formed againbetween adjacent electrode bodies. This may require the furtherelectrical connection of the adjacent electrode body to the secondterminal 140, if the electrical connection did not already exist, so asto create the anodic potential on that body. For example, in FIG. 9,once fuel growth on electrode body 12 a causes a short with electrodebody 12 b, switch 180 is opened so that both electrode body 12 a and,through the electric connection of the fuel growth, electrode body 12 b,have the cathodic potential. On the other hand, switch 190 closes (if itwas not already closed before), such that at least electrode body 12 chas an anodic potential, thus maintaining the adjacent electrode bodyseparation for the potential difference between the electrode(s) havingthe cathodic potential and the electrode(s) having the anodic potential.

The progressive shifting of which electrodes have the cathodic potentialand which electrodes have the anodic potential may continue throughoutthe cell 10, with the opening of switches 190 and 200, until no furtherprogression is desired or possible. For example, in the illustratedembodiment, wherein there is a separate charging electrode 70, theprogression will end when the separate charging electrode 70 is the onlyelectrode body having the anodic potential, and all permeable electrodebodies 12 a-12 d of the fuel electrode 12 have the cathodic potential.Charging of the cell 10 may subsequently end when fuel growth onelectrode body 12 d causes an electrical connection between electrodebody 12 d and charging electrode 70. In an embodiment, the switchingsystem 70 may be configured to have an over-charge configuration,wherein the cell may be configured to selectively apply a cathodicpotential to charging electrode 70 by opening switch 170, and closingswitch 160, applying the anodic potential to the oxidant electrode 14,utilizing it for further charging of cell 10 by permitting fuel growthon the charging electrode 70.

Charging of the cell 10 may in various embodiments progress fromelectrode body to electrode body among the plurality of permeableelectrode bodies 12 a-12 d, or may end based on criteria such as thevoltage, current, slope of voltage, slope of current, charge capacity,or value of impedance or resistance. Such measurements in variousembodiments may be taken over one or more of the electrode bodies 12a-12 d, or across one or more cells 10. In an embodiment, charging mayend based on a sensing electrode placed between the charging electrodeand the last permeable electrode body 12 d of the fuel electrode 12.

During discharge of the cell 10 in the embodiment of FIG. 9, oxidantelectrode switch 160 would be closed, while charging electrode switch170 would be open. Additionally, switches 180, 190, and 200 would beopen, and fuel consumption would be from electrode body 12 d toelectrode body 12 a, wherein the electrical connection between theelectrode bodies 12 a-12 d are through the fuel growth. In theillustrated embodiment, this is so electrode bodies 12 a-12 d are notshorted to the oxidant electrode 14 by oxidant electrode switch 160.

Continuing to FIG. 10, another embodiment of switching system 60 isillustrated for the cell 10. Again there is the bypass switch 150,configured to connect first terminal 130 directly to second terminal140, bypassing the cell 10. The switching system 60 also includes aseries of connecting switches 210 a-d, configured to selectively andprogressively connect each of the electrode bodies 12 b-d to either thefirst terminal 130 or the second terminal 140, such that each of theelectrode bodies 12 b-d either has a cathodic potential (i.e. isconnected to at least electrode body 12 a) or an anodic potential (i.e.is connected to at least charging electrode 70). As shown, duringcharging, bypass switch 150 would be open so the cell is not bypassed.Oxidant electrode switch 160 would also be open, so that oxidantelectrode 14 is disconnected during the charging process. Chargingelectrode switch 170 would be closed so that at least charging electrode70 would have an anodic potential. To promote minimal distance betweenthe electrode(s) having the cathodic potential (initially just electrodebody 12 a) and the electrodes having the anodic potential, switches 210b, 201 c, and 210 d would be closed, so that the anodic potentialcreated through the electrical connection to second terminal 140 isapplied through electrode bodies 12 b-12 d, as well as chargingelectrode 70. As fuel growth on electrode body 12 a progresses, it willeventually contact electrode body 12 b. In an embodiment, at that timeswitch 210 b would open, so that electrode bodies 12 a-12 b have thecathodic potential, while electrode bodies 12 c-12 d and chargingelectrode 70 have the anodic potential. In an embodiment, switch 210 awould also be closed, so that a stronger electrical connection betweenelectrode bodies 12 a-12 b is formed, beyond the electrical connectionof the fuel growth. Such progression could continue, as above, with theopening of switches 210 c and 210 d respectively, as the number ofelectrode bodies having the anodic potential shrinks, while the numberof electrodes having the cathodic potential grows. Again, in someembodiments switches 210 b and 210 c could close in progression, to forma stronger electrical connection between electrode bodies 12 a-12 d asthe number of electrodes having a cathodic potential progressivelygrows.

During discharge of the cell 10 in the embodiment of FIG. 10, oxidantelectrode switch 160 would be closed, while charging electrode switch170 would be open. In an embodiment switches 210 a-210 d could remainopen and fuel consumption would be from electrode body 12 d to electrodebody 12 a, wherein the electrical connection between the electrodebodies 12 a-12 d are through the fuel growth. In another embodiment,switches 210 a-210 d could be closed, so that an electrical connectionis between all electrode bodies 12 a-12 d of the fuel electrode 12, andfuel is oxidized throughout the fuel electrode 12 while an oxidant isreduced at the oxidant electrode 14. This is permissible in thisembodiment because opening switch 170 also prevents the electrode bodies12 a-d from being shorted to the oxidant electrode 14 by oxidantelectrode switch 160.

Another embodiment of the switching system 60 for the cell 10 is seen inFIG. 11. Once more, the switching system 60 comprises the bypass switch150, configured to selectively connect the first terminal 130 directlyto the second terminal 140, in order to bypass the cell 10. Theswitching system 60 of the embodiment of FIG. 11 also includes anotherseries of connecting switches 220 a-d, configured to selectively connecteach of the electrode bodies 12 a-d to the charging electrode 70. Again,the switching system 60 may be configured to allow progressive change ofthose electrodes having the cathodic potential (i.e. at least electrodebody 12 a) and those electrodes having the anodic potential (i.e. atleast charging electrode 70). As shown, during charging, bypass switch150 would be open so the cell is not bypassed. Oxidant electrode switch160 would also be open, so that oxidant electrode 14 is disconnectedduring the charging process. Charging electrode switch 170 would beclosed so that at least charging electrode 70 would have an anodicpotential. Switch 220 a would be opened so that the cell is not bypassedfrom first terminal 130 to second terminal 140 through switch 220 a andswitch 170. To promote minimal distance between the electrode(s) havingthe cathodic potential (initially just electrode body 12 a) and theelectrodes having the anodic potential, at least switch 220 b would beclosed, so that at least electrode bodies 12 b, as well as chargingelectrode 70, have the anodic potential. As fuel growth on electrodebody 12 a progresses, it will eventually contact electrode body 12 b. Inan embodiment, at that time switch 220 b would open, so that electrodebodies 12 a-12 b have a cathodic potential (connected through the fuelgrowth). Switch 220 c would then close, if it was not closed before, sothat at least electrode body 12 c, as well as charging electrode 70,would have the anodic potential. Such progression could continue, asabove, with the opening of switches 210 c and 210 d respectively, as thenumber of electrode bodies having the anodic potential shrinks, whilethe number of electrode bodies having the cathodic potential grow.

During discharge of the cell 10 in the embodiment of FIG. 11, oxidantelectrode switch 160 would be closed, while charging electrode switch170 would be open. In an embodiment switches 220 a-220 d could remainopen and fuel consumption would be from electrode body 12 d to electrodebody 12 a, wherein the electrical connection between the electrodebodies 12 a-12 d are through the fuel growth therebetween.

The progressive shifting of which electrode bodies have a cathodicpotential versus which electrode bodies have an anodic potential may beanalogized as the cell 10 having N electrode bodies defining twoconceptual electrodes, a cathodic potential electrode and an anodicpotential electrode. In the cell, the constituent makeup of the cathodicpotential electrode may begin with a single electrode body, while theanodic potential electrode may comprise at least the adjacent electrodebody, up to all other electrode bodies. During charging, fuel grows onthe cathodic potential electrode until, for example, no further growthon the electrode body is possible (i.e. the cathodic potential electrodehas shorted to the anodic potential electrode). At that time, theelectrode body of the anodic potential electrode that is adjacent to thecathodic potential electrode is reassigned to become part of thecathodic potential electrode, through an electrical connection formed bythe fuel growth and/or through the use of electrical circuitry orswitches associated with the electrode bodies of the cell. With thereassignment, the cathodic potential electrode now comprises twoelectrode bodies, while the anodic potential electrode has one less thanits initial number of electrode bodies. As a potential difference mayresume between the cathodic potential electrode and the anodic potentialelectrode, fuel growth from charging may resume, again until, forexample, no further growth on the electrode bodies of the cathodicpotential electrode is possible.

The progressive shifting of the constituent makeup of the cathodicpotential electrode and the anodic potential electrode may continuethroughout the cell, for example with the opening and/or closing ofswitches associated with the electrode bodies, until no furtherprogression is desired or is possible. For example, once the anodicpotential electrode comprises only a single electrode body, no furtherprogression is possible. The charging of the cell may subsequently endwhen fuel growth on the cell causes an electrical connection to formbetween the conceptual cathodic potential electrode and the conceptualanodic potential electrode that comprises only a single electrode body.

Again, in various embodiments charging of the cell 10 may progress fromelectrode body to electrode body among the plurality of permeableelectrode bodies 12 a-12 d, or may end based on criteria such as thevoltage, current, slope of voltage, slope of current, charge capacity,or value of impedance or resistance. Such measurements in variousembodiments may be taken over one or more of the electrode bodies 12a-12 d, or across one or more cells 10. In an embodiment, charging mayend based on a sensing electrode placed between the charging electrodeand the last permeable electrode body 12 d of the fuel electrode 12.

As noted previously, in an embodiment, multiple electrochemical cells 10may be combined in cell system 100. Shown in FIGS. 12A-C areelectrochemical cell systems 100 of the embodiments of FIGS. 9-11,however comprising N electrochemical cells 10. The number N is anyinteger greater than or equal to two, and is not limited to anyparticular number. As illustrated, the bypass switches 150 in theswitching systems 60 of each cell 10 are configured to selectivelybypass each cell 10 by providing a direct connection between the firstterminal 130 and the second terminal 140. Such a connection may again beused to bypass defective cells 10, or for any other reason. Also, invarious embodiments of cell systems 100, different embodiments of theswitching system 60 (such as those found in FIGS. 9-11) may be used inconjunction with one another in a single cell system 100.

In any embodiment, the switches of the switching system 60 (or any otherswitch described herein) may be of any type, and the term switch isbroadly intended to describe any device capable of switching between themodes or states described. For example, in some non-limitingembodiments, the switches may be single pole single throw or single poledouble throw. They may be of the pivoting, sliding or latching relaytype. Also, semiconductor based switches may be used as well. Theswitches may be activated electrically (electromechanical relay) ormagnetically or by other methods known to those familiar in the art. Anyother suitable type of switch may be used, and the examples herein arenot limiting. In an embodiment, the plurality of switches may beconnected in series if the switch has a leakage current in onedirection. For example, the body diode of a MOSFET semiconductor basedswitch will conduct in one direction and the leakage current can beeliminated by placing MOSFET semiconductor based switches facing back toback in series.

Any suitable control mechanism may be provided to control the action ofswitches in the switching system 60 and/or the terminal selector system62. As shown in FIG. 13, in an embodiment the switches of the switchingsystem 60 may be controlled by a controller 230. The controller 230 maybe of any construction and configuration. In an embodiment, thecontroller 230 may be configured to manage application of the anodicpotential from the power supply PS to permeable electrode bodies 12 b-dand the charging electrode 70. The controller 230 may causeelectrodeposition of metal fuel, through reduction of reducible ions ofthe metal fuel from the ionically conductive medium, to progressivelygrow from permeable electrode body 12 a to each subsequent electrodebody 12 b-d for application of a cathodic potential to each subsequentlyconnected electrode body 12 b-d. The controller 230 may also causeremoval of the anodic potential from each subsequently connectedelectrode body, and may cause application of the anodic potential to atleast the subsequent electrode body unconnected by theelectrodeposition, or the charging electrode where the last electrodebody (i.e. electrode body 12 d) has been electrically connected by theelectrodeposition to the prior electrode bodies 12 a-c. Such applicationof the anodic potential may be configured to permit or cause oxidizationof an oxidizable species of the oxidant.

In an embodiment, the controller 230 may comprise hard-wired circuitry232 that manipulates the switches based on an input 234 determining theproper switch configuration. The controller 230 may also include amicroprocessor for executing more complex decisions, as an option. Insome embodiments, the controller 230 may also function to manageconnectivity between the load L and the power source and the first andNth cells (i.e. may control the terminal selector system 62 describedabove). In some embodiments, the controller 230 may include appropriatelogic or circuitry for actuating the appropriate bypass switches 150 inresponse to detecting a voltage reaching a predetermined threshold (suchas drop below a predetermined threshold). In some embodiments, thecontroller 230 may further comprise or be associated with a sensingdevice 236, including but not limited to a voltmeter (digital or analog)or potentiometer or other voltage measuring device or devices, that canbe used to determine when to modify the configuration of the pluralityof switches, such as to maintain the proximity of the anode and thecathode as fuel growth progresses during charging. In some embodiments,the sensing device 236 may instead measure current, resistance, or anyother electrical or physical property across or of the cell 10 that maybe used to determine when to modify the configuration of the pluralityof switches. For example, the sensing device 236 may measure a spike incurrent or a drop in potential difference between two electrode bodies.In some embodiments, the controller 230 may control the switches of theswitching system 60 based on the passage of increments of time. Forexample, in an embodiment the time for fuel growth to progress betweenadjacent electrode bodies may be known, and used to calculate when tooperate the switching system 60 so as to progressively rewire theelectrodes to maintain an adjacent separation between the anode and thecathode. In an embodiment, the controller 230 may control the switchesof switching system 60 to provide a high efficiency mode for the cell,such as is disclosed in U.S. Provisional Patent Application 61/323,384,now pending as U.S. patent application Ser. No. 13/083,929, each ofwhich is incorporated in its entirety herein by reference.

In some embodiments, the controller 230 may be configured to selectivelyenter different charging modes. For example, in one mode a plurality ofelectrode bodies may initially have an anodic potential, but the numberdecreases as the electrode bodies are given a cathodic potential. Inanother mode, only a single electrode body has an anodic potential atany given time, and the electrode body with the anodic potential changesas prior electrode bodies are given the cathodic potential. For example,in the former mode, the controller 230 may close all switches associatedwith the charging electrode 70 and electrode bodies 12 b-d duringrecharge, such that an anodic potential is applied to each of electrodebodies 12 b-d and the charging electrode 70. The controller 230 may thenprogressively open the switches associated with each of electrode bodies12 b-d as the electrode bodies 12 b-d progressively become electricallyconnected to electrode body 12 a, and thus have a cathodic potential. Inthe latter mode, the controller may initially close only the switchassociated with electrode body 12 b, giving electrode body 12 b ananodic potential while electrode body 12 a has a cathodic potential.When fuel growth on electrode body 12 a reaches electrode body 12 b,creating an electrical connection therebetween, the controller 230 mayopen the switch associated with electrode body 12 b that gave electrodebody 12 b the anodic potential, such that electrode body has a cathodicpotential through its electrical connection to electrode body 12 a. Thecontroller 230 may then proceed to close the switch associated withelectrode body 12 c, to provide electrode body 12 c with the anodicpotential, again creating a potential difference, and the progression offuel growth. These progressions of switch reassignments by thecontroller 230 may continue through or until only the charging electrode70 has the anodic potential, as is described above.

As seen in FIG. 14, another aspect of the present invention may includea method 240 for charging the electrochemical cell 10. Again,electrochemical cell 10 comprises the fuel electrode 12 comprising theplurality of permeable electrode bodies 12 a-d. Although four permeableelectrode bodies are listed, any number greater than or equal to two arepossible. The cell 10 further includes the oxidant electrode 14, and thecharging electrode, which may be the oxidant electrode 14 or theseparate charging electrode 70. The cell 10 additionally includes theionically conductive medium, and the switching system 60 comprising aplurality of switches, wherein at least some of the plurality ofswitches are associated with one of the permeable electrode bodies 12a-d, the oxidant electrode 14, and the charging electrode (i.e. oxidantelectrode 14 or separate charging electrode 70). During a charging mode,reducible fuel ions in the ionically conductive medium are reduced andelectrodeposited as fuel in oxidizable form on a cathode comprising atleast permeable electrode body 12 a while an oxidant is oxidized on ananode comprising at least an adjacent one of the permeable electrodebodies 12 b-d and/or the charging electrode (i.e. charging electrode70).

The method 240 starts at 250, and includes at 260 electricallyconnecting the cathode (i.e. in an embodiment, initially just permeableelectrode body 12 a), distal from the charging electrode, to thenegative terminal of power supply PS, and the anode (i.e. initially atleast permeable electrode body 12 b) to the positive terminal of thepower supply PS, creating a potential difference therebetween. Themethod 240 continues at 270, wherein, the fuel is electrodeposited onthe cathode (i.e. at least permeable electrode body 12 a). As seen instep 280, the method 240 may continue by determining if fuel growth hasprogressed to beyond a threshold amount. In an embodiment the thresholdamount may be ascertained when the cell 10 is shorted by the fuel growthcreating an electrical connection through the fuel growth between thecathode (i.e. permeable electrode body 12 a) and the anode (i.e.permeable electrode body 12 b). As shown, if fuel growth has not reachedthe threshold amount, the growth of fuel at 270 is repeated. Once thethreshold amount is reached, the method continues at 290, wherein it maybe determined if further fuel growth is both possible and desired. In anembodiment, the determination at 290 may include ascertaining if thereare additional electrode bodies, such as permeable electrode bodies 12c-d, that fuel growth may be possible on. If so, the method continues at300 by using the plurality of switches of the switching system 60 todisconnect the connecting electrode body (i.e. permeable electrode body12 b) from the anode, and if it were not connected through the switchingsystem 60 before, connecting the next adjacent electrode body (i.e.permeable electrode body 12 c) to the anode. This creates the potentialdifference between the cathode (now comprising permeable electrodebodies 12 a-b) and the anode (comprising at least permeable electrodebody 12 c). The method 240 then returns to 270 wherein fuel growthcontinues on the cathode. If no further fuel growth is possible ordesired at 290, the method 240 continues to 310 by disconnecting atleast the negative terminal of the power source PS from the cell 10 todiscontinue the charging process. The method 240 may then end at 320.

Shown in FIG. 15, another aspect of the present invention may include amethod 330 for discharging the electrochemical cell 10, which may besimilar to that described above as related to FIG. 14. During thedischarge mode, fuel on permeable electrode bodies 12 a-12 d is oxidized(and thus is consumed into the ionically conductive medium as reduciblefuel ions), while an oxidizer is reduced at the oxidant electrode 14.

The method 330 starts at 340, and includes at 350 using the plurality ofswitches of the switching system 60 to connect the permeable electrodebodies 12 a-d that contain fuel. In an embodiment, if the cell 10 iscompletely charged all permeable electrode bodies 12 a-d would beelectrically connected to one another. As the cell 10 is in dischargemode, the plurality of switches of the switching system 60 would beconfigured to electrically disconnect the separate charging electrode 70(if present). In an embodiment, the method 330 would continue at 360 byelectrically connecting the cathode (i.e. the air cathode, oxidantelectrode 14) to the negative terminal of load L, and the anode (i.e.the fuel electrode 12, containing the electrically connected permeableelectrode bodies 12 a-d) to the positive terminal of the power supplyPS, creating a potential difference therebetween. The method 330continues at 370, wherein the fuel is consumed on the fuel electrode 12.In an embodiment, because the plurality of switches 60 connect thepermeable electrode bodies 12 a-d, an anodic potential is applied toeach of the permeable electrode bodies 12 a-d, and fuel may be consumedfrom each or any of permeable electrode bodies 12 a-d. As seen in step380, the method 330 may continue by determining if consumable fuel hasbeen depleted from any permeable electrode body 12 a-d. In anembodiment, a sensor, such as the sensing device 236 above, which mayinclude a current or a voltage sensor, may be present in the cell 10,and may indicate when consumable fuel has been depleted from one or moreof the permeable electrode bodies 12 a-d. If no depletion is detected,the discharging may continue as method 330 returns to step 370. If,however, consumable fuel has been depleted from one or more of permeableelectrode bodies 12 a-d, then method 330 may continue to step 390,wherein it may be determined whether there are any remaining permeableelectrode bodies 12 a-d that contain consumable fuel. This determinationmay be made simultaneously with the determination of depletion in step380, and may be made through a survey of sensing device(s) 236, or byany other appropriate method.

If consumable fuel remains on one or more of permeable electrode bodies12 a-d, the method 330 may continue at step 400, wherein the switchingsystem 60 adjusts the plurality of switches so that any of permeableelectrode bodies 12 a-d that lack consumable fuel are disconnected fromfuel electrode 12. In an embodiment, consumption of fuel may initiallybe from the electrode body that is closest to the oxidant electrode 14(such as, for example, permeable electrode body 12 d in the illustratedembodiments above), and switching system 60 may disconnect permeableelectrode body 12 d, 12 c, and 12 b in that order, until all fuel isconsumed from permeable electrode body 12 a. Once none of the permeableelectrode bodies 12 a-d contain consumable fuel, or further dischargingis no longer desired (or possible), the method may continue to step 410,wherein the load L may be disconnected. In an embodiment, the load L mayremain connected to the cell 10 when it is depleted, until the cell 10is recharged, in which case it may be disconnected so that the cell 10may be connected instead to the power supply PS. The method 330 may thenend at 420.

FIG. 16 depicts another embodiment of the cell 10. As shown, theembodiment of cell 10 in FIG. 16 has the fuel electrode 12 with fiveelectrode bodies 12 a-e. Cell 10 further has a separate chargingelectrode 70 (i.e. a dedicated OEE), and an oxidant electrode 14. As inthe above embodiments, cell 10 includes a switching system 60 configuredto selectively connect these electrodes and electrode bodies to one ofthe first terminal 130 or the second terminal 140. The switching system60 may include the controller 230, configured to control the pluralityof switches connected to it through circuitry 232. As shown, thecontroller 230 may have the sensing device 236 included within it.Controller 230 may also receive instructions through the input 234regarding how to control the switches.

As in the above embodiments, the cell 10 may have the bypass switch 150configured to connect first terminal 130 directly to second terminal140, bypassing the cell 10 in cases such as where a fault is presentwithin the cell 10, or for any other reason where utilization of thecell 10 is not desired. The oxidant electrode 14 is again selectivelyconnected to the second terminal 140 for discharging by oxidantelectrode switch 160, and the separate charging electrode 70 is againselectively connected to the second terminal 140 for charging by thecharging electrode switch 170. In the illustrated embodiment, theelectrode bodies 12 b-e may be selectively connected to either the firstterminal 130 or the second terminal 140 by electrode body switches 425b-e, where “b” through “e” indicate which of electrode bodies 12 b-e areassociated with the respective switch. As is shown in the illustratedembodiment, electrode body switches 425 b-e are configured toalternatively connect each of electrode bodies 12 b-e to either a firstbus 427 a associated with electrode body 12 a (and thus first terminal130), or a second bus 427 b associated with the separate chargingelectrode 70 (and thus second terminal 140 through charging electrodeswitch 170). In an embodiment, electrode body switches 425 b-e may becharacterized as Single Pole, Double Throw. In some embodiments,electrode body switches 425 b-e may have three alternative settings,such that each electrode body 12 b-e may be electrically connected toelectrode body 12 a (and first terminal 130), separate chargingelectrode 70, or disconnected from both electrode body 12 a and separatecharging electrode 70. In an embodiment, such electrode body switches425 b-e may be characterized as Single Pole, Triple Throw.

During charging of the electrochemical cell 10, power is applied from apower supply between first terminal 130 and second terminal 140. Bypassswitch 150 would be open so that there is no short between firstterminal 130 and second terminal 140. Since the cell 10 is in a chargingmode, the oxidant electrode 14 is not utilized, so oxidant electrodeswitch 160 is also open. Accordingly, during charging the chargingelectrode switch 170 would be closed. As each of electrode bodies 12 b-emay be selectively coupled to the anode or the cathode in thisembodiment, charging techniques such as but not limited to theprogressive OEE described above, or that disclosed in U.S. ProvisionalPatent Application No. 61/383,510 and U.S. patent application Ser. No.13/230,549, each of which is incorporated herein in its entirety byreference, may be utilized. The operation of electrode body switches 425b-e in some embodiments is discussed in greater detail below.

Turning now to the flowchart in FIG. 17, another aspect of the presentinvention may include an algorithm 430 associated with different chargemodes for the electrochemical cell 10. Although description of theoperation of the algorithm 430 will be made with reference to theembodiment of the cell 10 in FIG. 16, the algorithm 430 may beimplemented onto any suitable embodiment of the electrochemical cell 10by any appropriate mechanism. In one non-limiting embodiment, instead ofutilizing the electrode body switches 425 b-e, a more complexmultiplexing switching system 60 may be utilized. In anothernon-limiting embodiment, a plurality of Single Pole, Single Throwswitches may be configured in an array to allow for electricalconnection or isolation between any two or more of electrode bodies 12a-e and separate charging electrode 70. Any suitable system forelectrically connecting electrode bodies 12 a-e and/or separate chargingelectrode 70 may be utilized.

In an embodiment the algorithm 430 may include instructions, such ascomputer interpretable or readable instructions, that may program orotherwise control the controller 230. In some embodiments, the algorithm430 may be located on a system that is networked with or otherwiseconnected to controller 230. In some embodiments, the algorithm 430 maybe stored on a medium within controller 230, or within any othercontroller that may allow programmatic control of the switches inswitching system 60.

As shown, algorithm 430 may be configured, at 440, to select aparticular charge mode for the cell 10. The selection of the charge modemay be made by any appropriate determination criteria 450. For example,in an embodiment the determination criteria 450 may include measurements460 of the cell 10. The measurements 460 of the cell 10 may be anyappropriate measure of the status of the cell, including but not limitedto sensor readings pertaining to the current status of fuel growth onpermeable electrode bodies 12 a-e, readings of the current electricalconnections formed by the switching system 60, measurements of a voltageand/or current from or through the cell 10, or so on. To ascertainmeasurements 460, controller 230 may utilize sensing device 236, whichin the current embodiment shows leads extending across the cell 10,between first terminal 130 and second terminal 140.

Measurements 460 may also include measures of the environment. In oneembodiment, measurements 460 of the environment may include ascertainingthe current time. For example, where the cell 10 is associated with asolar power system, charging earlier in the day may utilize a differentcharge mode than charging when the sun is closer to setting. Othermeasurements 460 of the environment are also possible. For example, insome non-limiting embodiments, measurements 460 may be of theenvironmental temperature, weather conditions, ambient light, movementof the cell 10 (i.e. if the cell 10 is utilized in a vehicle, differentcharge modes may be utilized for different speeds or braking styles), orso on.

Determination criteria 450 may also include manual overrides 470, whichmay include any form of manual selection as to which charge mode isdesired. Such a manual selection for manual overrides 470 may, in anembodiment, be provided to the controller 230 by input 234. In anembodiment, determination criteria 450 may also include limits 480,which for example may determine an appropriate charge mode based onexceeding predefined tolerances or settings. For example, limits 480 maybe based on the measurements 460, and include, for example, voltagedifference between electrodes or electrode bodies, current impedancebetween electrodes or electrode bodies, or so on. In variousembodiments, limits 480 may be based on voltage, current, slope ofvoltage, slope of current, charge capacity, or value of impedance orresistance, for example. Such limits 480 may be based on measurements460 on or across one or more electrode bodies 12 a-e, or on or acrossone or more cells 10.

Once the charge mode is selected at 440, the controller 230 may identifythe charge mode at 490, and proceed to charge the cell 10 accordingly.Although in an embodiment the charge mode may be one which utilizes aprogressive OEE, such as that described above, in the illustratedembodiment the controller 230 is configured to select from twoalternative charge modes, a progressive charge mode 500, and a parallelcharge mode 600. In other embodiments, additional or alternative chargemodes may be utilized, and may be in accordance with the algorithm 430.

As shown in the illustrated embodiment, progressive charge mode 500 is ahigh capacity charge mode. This implies that the cell 10 is configuredto be charged in a manner that provides a significant amount of densityin the fuel growth between electrode bodies 12 a-e. In some embodiments,this high capacity charge mode may take a longer interval of time tocomplete the charging process, but may enable the greatest amount ofenergy storage within the cell 10. Such a charging mode may be usefulfor a number of applications, including but not limited to emergencybackup power and uninterruptible power supplies, where a larger amountof power may be needed, and a relatively large amount of time isavailable to recharge the cell 10 following its use. In suchapplications the amount of energy stored in cells 10 is of greaterimportance than the charging rate. Because the charging process isroughly serial between the electrode bodies of the fuel electrode 12,the charging rate is slower than in other embodiments. In theillustrated embodiment, wherein the cell 10 has five electrode bodies 12a-e in the fuel electrode 12, and a separate charging electrode 70 (i.e.the dedicated oxygen evolving electrode, or OEE), the progressivecharging mode 500 may include five phases.

When the cell 10 is uncharged, the progressive charge mode 500 may beginat a first phase 505, wherein only the first electrode body 12 a formsthe cathode, while electrode bodies 12 b-e and the separate chargingelectrode 70 form the charging electrodes. In the embodiment of FIG. 16,the first phase 505 would have electrode body switches 425 b-econnecting electrode bodies 12 b-e to the separate charging electrode 70through second bus 427 b, which would be connected to second terminal140 through charging electrode switch 170. As such, only electrode body12 a would be electrically connected to first terminal 130, creating apotential difference between electrode body 12 a and the group ofcharging electrodes formed by the electrode bodies 12 b-e and theseparate charging electrode 70. Fuel growth would then proceed onelectrode body 12 a towards the adjacent electrode body 12 b.

Once the fuel growth reaches a sufficient amount that electrode body 12a and electrode body 12 b short together at 510, the progressive chargemode 500 would proceed to a second phase at 515, wherein electrodebodies 12 a-b form the cathode, while electrode bodies 12 c-e and theseparate charging electrode 70 form the charging electrodes. In theembodiment of FIG. 16, the second phase 515 would have electrode bodyswitch 425 b disconnect electrode body 12 b from the group of chargingelectrodes on second bus 427 b, and electrically connect it to electrodebody 12 a through first bus 427 a. The determination that electrodebodies 12 a-b have shorted at 510 may be made through any suitablemechanism. For example, the sensing device 236 associated withcontroller 230 may measure a voltage drop or a current spike across thecell 10. In other embodiments, other sensing devices 236 may ascertainthe electrical connection, indicating the need to proceed to the secondphase at 515.

As fuel growth progresses through the cell 10, the progressive chargemode 500 may electrically disconnect the contacting electrode body 12b-e from the second bus 427 b, and connect it instead to the first bus427 a, progressively reassigning it form a charging electrode to acathode. In embodiments wherein electrode body switches 425 b-e areSingle Pole, Triple Throw, the electrode body switches 425 b-e mayeither be configured to connect contacting electrode bodies 12 b-e alongfirst bus 427 a, or the electrode body switches 425 b-e may move totheir electrically disconnected position, such that their electricalconnection to first terminal 130 is through the fuel growth alone. Asdepicted in the flowchart of FIG. 17, progressive charge mode 500continues at 520 with determining the shorting of electrode bodies 12b-c, before proceeding to a third phase at 525, where electrode body 12c would be disconnected from electrode body 12 d, such as by thethrowing of electrode body switch 425 c. Fuel growth progresses untilthe shorting between electrode bodies 12 c-d at 530. At that time, afourth phase would begin at 535, with electrode body 12 d beingelectrically disconnected from electrode body 12 e, such as by thethrowing of electrode body switch 425 d, connecting electrode body 12 dwith the first bus 427 a. At 540, the fuel growth progression toelectrically short electrode bodies 12 d and 12 e is determined, and afifth phase 545 begins, where electrode body 12 e is electricallydisconnected from the separate charging electrode 70, such as by thethrowing of electrode body switch 425 e, connecting electrode body 12 ewith the first bus 427 a, such that none of the charging electrodes 12b-3 are connected to the separate charging electrode 70 through thesecond bus 427 b.

Once all electrode bodies 12 b-e are connected with electrode body 12 a,by the fuel growth through electrode bodies 12 a-e and/or electricalconnections through the first bus 427 a, the fuel may continue to growon electrode body 12 e towards the separate charging electrode 70, dueto the potential difference between those electrodes. Eventually, at550, it may either be determined that electrode body 12 e has shortedwith the separate charging electrode 70, indicating maximum fuel growththroughout the cell 10, or a threshold charge capacity has been reached.Such a threshold capacity may be defined so that the cell does not“over-charge.” For example, in some embodiments it may be undesirablethat fuel growth reach and form an electrical connection to the separatecharging electrode 70. In an embodiment, the threshold charge capacitymay be approximately 80-100% of the maximum possible charge capacity forthe cell 10. The measurement of capacity may be made by any suitablemechanism, including in some embodiments taking measurements with thesensing device 236, or computing or estimating a charge capacity throughcontroller 230. Regardless, once the threshold capacity has beenreached, or electrode body 12 e has shorted with the separate chargingelectrode 70, the cell may enter an idle state, to await a futuredischarge mode.

If during the selection of the charge mode at 440, a desire for a fastercharge is indicated, the parallel charge mode 600 may be selected at490. In the parallel charge mode 600, mini-cells may be formed withinthe cell 10, with alternating bodies between electrode body 12 a and theseparate charging electrode 70 acting as either an anode or a cathode.In an embodiment, the parallel charge mode 600 may be N times fasterthan progressive charge mode 500 (where N is the number of electrodebodies that metal fuel is being plated on). In an embodiment, the growthrate on a given electrode body is limited by the diffusion-limitedcurrent density of the metal fuel deposition, which is affected by anumber of factors, including viscosity, concentration, diffusity, and soon. Although the parallel charge mode 600 would be faster than theprogressive charge mode 500, the fuel growth may be potentially lessdense than in the progressive charge mode 500, because the total chargedeposited is limited by the time taken for electrical connections toform between all electrode bodies. In some embodiments, the energydensity held by the cell 10 charged by the parallel charge mode 600 maybe ¼ to ½ that of the cell 10 charged by the progressive charge mode500. Some examples of applications that would prefer the parallel chargemode 600 may include, for example, electric vehicles such as forkliftsor cars, where a faster charge rate may be of greater importance than alarger charge density, like when the vehicle is being continuously usedin close proximity to charging opportunities.

In an embodiment, the parallel charge mode 600 may begin at a firstphase 605, with electrode bodies 12 a, 12 c, and 12 e connected to thefirst terminal 130, while electrode bodies 12 b and 12 d, as well as theseparate charging electrode 70, are connected to the second terminal140. In the embodiment of FIG. 16, to connect electrode bodies 12 c and12 e to the first terminal 130, such that electrode bodies 12 a, 12 c,and 12 e are the initial cathodes during charging, electrode bodyswitches 425 c and 425 e may initially be controlled to connectelectrode bodies 12 c and 12 e to the first bus 427 a. Likewise, forelectrode bodies 12 b and 12 d to be initially coupled to the secondterminal 140, so that electrode bodies 12 b and 12 d (like separatecharging electrode 70) are anodes during charging, electrode bodyswitches 425 b and 425 d may be controlled to connect electrode bodies12 b and 12 d to the second bus 427 b, where they are electricallyconnected to the second terminal 140 by charging electrode switch 170,which is closed during charging.

As charging progresses during the first phase 605 of the parallel chargemode 600, fuel growth may be bi-directional on the intermediateelectrode bodies 12 c and 12 e that are acting as cathodes. In theembodiment of FIG. 16, metal fuel is initially growing on electrode body12 a towards electrode body 12 b, due to the potential differencetherebetween. Fuel is also growing on electrode body 12 c both towardselectrode body 12 b and towards electrode body 12 d Likewise,bidirectional fuel growth is occurring on electrode body 12 e, towardsboth electrode body 12 d and the separate charging electrode 70. Duringthe charging, there may be, at 610, a number of continuity tests.Specifically, for N electrode bodies, there may be N−1 continuity testsperformed to determine if an electrical connection has formed betweenany of the anodes and any of the cathodes. For example, at 610 a, it maybe determined if electrode body 12 a has shorted to electrode body 12 bLikewise, at 610 b, it may be determined if an intermediate electrodebody (i.e. electrode body 12 c-d in the illustrated embodiment) hasshorted with either of the electrode bodies adjacent to it.Additionally, at 610 c, it may be determined if the last electrode body(i.e. the “N−1”^(th) electrode, which is electrode body 12 e in FIG. 16)has shorted with the separate charging electrode 70.

If any of the continuity tests at 610 indicate an electrical connectionhas formed between an anode and a cathode, the parallel charge mode 600may progress to an iterative next phase at 615, wherein any shortedcharging electrode (i.e. electrode body 12 b or electrode body 12 d) iselectrically disconnected from the second terminal 140. For example, ifany short occurs between the first bus 427 a and the second bus 427 b,whichever of the switches 425 b-e that can be thrown to eliminate thatelectrical connection may be thrown accordingly.

In an embodiment, any of the intermediate electrode bodies 12 b-e may bereassigned from acting as anodes to acting as cathodes, or vice versa,based on the electrical connections formed during the parallel chargemode 600. For example, if fuel growth electrically connects electrodebody 12 c (as a cathode) to electrode body 12 d (as a chargingelectrode), while electrode body 12 e is still growing fuel, thecontroller 230 may assign the pair of fuel-linked electrode bodies 12c-d to act together as a charging electrode, in that both electrode bodyswitches 425 c-d connect electrode bodies 12 c-d to second terminal 140via second bus 427 b, so that bidirectional fuel growth of fuel onelectrode body 12 e continues. If fuel growth on electrode body 12 a haselectrically connected electrode bodies 12 a-b, then electrode body 12 bwould be electrically disconnected from second bus 427 b, such that apotential difference exists between electrode bodies 12 a-b andelectrode bodies 12 c-d, so that additional fuel growth can occur onelectrode bodies 12 a-b (as a cathode) towards electrode bodies 12 c-d(as a charging electrode).

If fuel growth on electrode body 12 e, which is initially a cathodeelectrically connected to first terminal 130 via electrode body switch425 e and first bus 427 a, causes a short with separate chargingelectrode 70, controller 230 may then throw electrode body switch 425 eto electrically disconnect electrode body 425 e from first bus 427 a,such that electrode body 12 e and the separate charging electrode 70, aswell as the metal fuel therebetween, all act as an interconnectedcharging electrode. If electrode body 12 d is then reassigned as acathode (due to electrical connection with electrode body 12 c, forexample), then fuel growth may continue from electrode body 12 d towardelectrode body 12 e, due to the potential difference therebetween.

In such a manner, the reassignment of electrode bodies 12 b-d mayprogress, measured by the continuity tests at 610, until, at 620, eitherall electrode bodies 12 a-e and the separate charging electrode 70 haveshorted, or a threshold capacity for the cell 10 has been reached.Again, the reaching of the threshold capacity may be ascertained by anysuitable mechanism, including in some embodiments taking measurementswith the sensing device 236, or computing or estimating a chargecapacity through controller 230. Regardless, once the threshold capacityhas been reached, or all electrodes in the cell 10 have shorted, thecell may end the parallel charge mode 600 and enter an idle state, toawait a future discharge mode.

In some embodiments, the controller 230 may be configured to charge thecell 10 such that some of the electrode bodies 12 a-e are charging inaccordance with progressive charge mode 500, while others of electrodebodies 12 a-e are charging in accordance with parallel charge mode 600.In some embodiments, the varying desires of charge rate and energydensity may be implemented in the charge mode selection at 440throughout the charging of the cell 10, such that the real time needs ofthe application utilizing the cell 10 may be taken into account. In anembodiment the controller 230 may measure typical dischargecharacteristics of the cell 10 over time, and modify the selection ofthe charge mode at 440 accordingly. As one non-limiting example, if thecell 10 is utilized in an electric vehicle that is utilizedintermittently during daylight hours, but is not utilized at night, thenthe controller 230 may utilize the parallel charge mode 600 to quicklycharge the vehicle as needed during the daylight, however may utilizethe progressive charge mode at night, so that the greater amount ofstored energy is held by the cell 10 for use the following day. In anembodiment, the controller 230 may be more sophisticated, and maycompute a more complex optimal energy vs. charge rate, to provide theoptimal quantity of run time based on the usage of the cell 10.

It may be appreciated that in some embodiments the controller 230 mayalso be configured to discharge the cell 10 in a variety of modes. Insome embodiments, the algorithm 430 may be further configured to selectbetween a charging mode and a discharging mode. In other embodiments, aseparate discharging algorithm may be provided for the discharge mode ormodes. In some embodiments, differing modes of charging and dischargingthe cell 10 may be managed by a broader “cell operations” algorithm,which may be run on controller 230, for example. In some embodiments,only the oxidant electrode 14 and a distal electrode body (i.e.permeable electrode body 12 a) are electrically connected to the load L,such that only the fuel electrically connects the permeable electrodebodies 12 a-e. During discharge, the fuel would progressively beconsumed from electrode body 12 e (proximal to the oxidant electrode14), towards the distal electrode body 12 a. Once fuel is sufficientlyconsumed from each of the intermediate permeable electrode bodies 12b-d, those bodies would electrically disconnect from the fuel electrode12 connected to the load L.

In some embodiments, the switching system 60 may be used to selectivelyconnect the permeable electrode bodies 12 b-e to the load L. In anembodiment, permeable electrode bodies 12 b-e may all be connected tothe load L throughout the discharging of the cell 10. In otherembodiments, control of which electrode bodies (i.e. permeable electrodebodies 12 b-e) are electrically connected to the load L may beascertained by the discharging algorithm, and may depend on a particulardischarge mode. In an embodiment, the determination to selectivelyconnect or disconnect the permeable electrode bodies 12 b-e from theload L may be based on measurements, manual overrides, or limits, whichmay be similar to those of determination criteria 450 that are used todetermine the charge mode at 440 described above. For example, thedecision to connect or disconnect one of the permeable electrode bodiesmay be based on criteria such as the voltage, current, slope of voltage,slope of current, charge capacity, or value of impedance or resistance.Such measurements in various embodiments may be taken over one or moreof the electrode bodies 12 a-12 e, or across one or more cells 10. In anembodiment, sensors such as sensing device 236 associated with one ormore of the electrode bodies 12 a-e and/or one or more of the cells 10may be utilized to take the measurements.

As above, in an embodiment the sensing device 236 may be, for example, avoltmeter (digital or analog), potentiometer, or other voltage measuringdevice or devices, which can be used to determine when to modify theconfiguration of the plurality of switches. In some embodiments, thesensing device 236 may instead measure current, resistance, or any otherelectrical or physical property across or of the cell 10 that may beused to determine when to modify the configuration of the plurality ofswitches. In some embodiments, the controller 230 may control theswitches of the switching system 60 based on the passage of incrementsof time. For example, in an embodiment the time for fuel consumptionbetween adjacent electrode bodies may be known, and used to calculatewhen to operate the switching system 60 so as to disconnect depletedones of the electrode bodies 12 b-e.

The foregoing illustrated embodiments have been provided solely toillustrate the structural and functional principles of the presentinvention, and should not be regarded as limiting. To the contrary, thepresent invention is intended to encompass all modification,substitutions, and alterations within the spirit and scope of thefollowing claims.

The subject matter claimed in the present application, owned by Fluidic,Inc., was developed as a result of activities undertaken within thescope of a license agreement qualifying as a joint research agreementunder 35 U.S.C. §103(c)(2) and (3) between Fluidic, Inc. and ArizonaScience and Technology Enterprises, LLC acting for the Board of Regentsfor and on behalf of Arizona State University, which was in effect priorto development of the claimed invention.

1. An electrochemical cell comprising: a fuel electrode comprising aseries of permeable electrode bodies arranged in spaced apart relation;an oxidant electrode spaced apart from the fuel electrode; a chargingelectrode selected from the group consisting of (a) the oxidantelectrode, (b) a third electrode spaced from the fuel electrode and theoxidant electrode, and (c) a portion of the fuel electrode; an ionicallyconductive medium contacting the electrodes; a controller coupled to aplurality of the electrode bodies of the fuel electrode, said controllerbeing configured to apply an electrical current between the chargingelectrode and at least one of the permeable electrode bodies with thecharging electrode functioning as an anode and the at least onepermeable electrode body functioning as a cathode, such that reduciblemetal fuel ions in the ionically conductive medium are reduced andelectrodeposited as metal fuel in oxidizable form on the at least onepermeable electrode body, so that said electrodeposition causes growthof the metal fuel among the permeable electrode bodies with theelectrodeposited metal fuel establishing an electrical connectionbetween the permeable electrode bodies, wherein said controller isconfigured to selectively apply the electrical current to a differentnumber of said permeable electrode bodies, each functioning as acathode, based on at least one input parameter so as to adjust a rateand density of the growth of the electrodeposited metal fuel.
 2. Anelectrochemical cell according to claim 1, wherein said controller isconfigured to select between: (1) a higher density progressive growthmode wherein the electrical current is applied to a terminal one of thepermeable electrode bodies with the charging electrode functioning asthe anode and the terminal electrode body functioning as the cathodesuch that the reducible metal fuel ions are reduced and electrodepositedas metal fuel in oxidizable form on the terminal permeable electrodebody, said electrodeposition causing growth of the metal fuel among thepermeable electrode bodies such that the electrodeposited metal fuelestablishes an electrical connection between the terminal electrode bodyand each subsequent permeable electrode body with said reduction anddeposition occurring on each subsequent permeable electrode body uponestablishment of said electrical connection; and (2) a higher rategrowth mode wherein the electrical current is applied simultaneously toa plurality of said electrode bodies with the charging electrodefunctioning as the anode and each of the plurality of electrode bodiesfunctioning as cathodes such that the reducible metal fuel ions arereduced and electrodeposited as metal fuel in oxidizable form on theterminal permeable electrode body, said electrodeposition causing growthof the metal fuel among the permeable electrode bodies.
 3. Anelectrochemical cell according to claim 2, wherein the controller isconfigured to apply the electrical current in the higher rate growthmode simultaneously to all the electrode bodies.
 4. An electrochemicalcell according to claim 2, wherein the controller is configured to applythe electrical current in the higher rate growth mode simultaneously toless than all the electrode bodies.
 5. An electrochemical cell accordingto claim 1, wherein said controller is configured to vary the number ofelectrode bodies to which the electrical current is applied whileperforming a recharging operation.
 6. An electrochemical cell accordingto claim 1, wherein the controller is coupled to a sensor that senses acondition of the electrochemical cell, and wherein the input parameteris input by the sensor.
 7. An electrochemical cell according to claim 1,wherein the input parameter is input via a user input.
 8. Anelectrochemical cell according to claim 1, wherein the input parameteris a limit parameter and wherein the controller is further configured tocompare a cell property to the limit parameter.
 9. An electrochemicalcell according to claim 8, wherein the cell property is a voltage, acapacity, an impedance between electrodes, a slope of electrodevoltages, a current, a resistance to a sensing electrode, or a shortingto the charging electrode.
 10. An electrochemical cell according toclaim 1, wherein the ionically conductive medium is an electrolyte. 11.An electrochemical cell according to claim 1, further comprising aplurality of switches operatively coupled between the controller and theplurality of electrode bodies, wherein the controller is configured tocontrol an open state and a closed state for each of the plurality ofswitches, to selectively apply the electrical current to some of theplurality of electrode bodies.
 12. An electrochemical cell according toclaim 2, wherein in the higher rate growth mode, the electrical currentis applied simultaneously to the plurality of electrode bodies such thatthe charging electrode comprises some of the plurality of electrodebodies functioning as anodes and the fuel electrode comprises some ofthe plurality of electrode bodies functioning as cathodes, and whereineach of the plurality of electrode bodies functioning as cathodes areseparated from one another by the plurality of electrode bodiesfunctioning as anodes.
 13. An electrochemical cell according to claim 1,wherein the controller is a charge/discharge controller.
 14. Anelectrochemical cell according to claim 2, wherein the controller is acharge/discharge controller.
 15. An electrochemical cell according toclaim 6, wherein the controller is a charge/discharge controller.
 16. Anelectrochemical cell according to claim 8, wherein the controller is acharge/discharge controller.
 17. An electrochemical cell according toclaim 12, wherein the controller is a charge/discharge controller.
 18. Amethod of recharging an electrochemical cell, wherein theelectrochemical cell comprises: a fuel electrode comprising a series ofpermeable electrode bodies arranged in spaced apart relation; an oxidantelectrode spaced apart from the fuel electrode; a charging electrodeselected from the group consisting of (a) the oxidant electrode, (b) athird electrode spaced from the fuel electrode and the oxidantelectrode, and (c) a portion of the fuel electrode; an ionicallyconductive medium contacting the electrodes; a controller coupled to aplurality of the electrode bodies of the fuel electrode, said controllerbeing configured to apply an electrical current between the chargingelectrode and at least one of the permeable electrode bodies with thecharging electrode functioning as an anode and the at least onepermeable electrode body functioning as a cathode, such that reduciblemetal fuel ions in the ionically conductive medium are reduced andelectrodeposited as metal fuel in oxidizable form on the at least onepermeable electrode body, so that said electrodeposition causes growthof the metal fuel among the permeable electrode bodies with theelectrodeposited metal fuel establishing an electrical connectionbetween the permeable electrode bodies, wherein said controller isconfigured to selectively apply the electrical current to a differentnumber of said permeable electrode bodies based on at least one inputparameter so as to adjust a rate and density of the growth of theelectrodeposited metal fuel; the method comprising: selecting, based onthe at least one input parameter, between a higher density progressivegrowth mode and a higher rate growth mode; charging the electrochemicalcell based on the selected one of the higher density progressive chargemode and the higher rate growth mode; wherein, in the higher densityprogressive growth mode, said charging comprises: applying theelectrical current to a terminal one of the permeable electrode bodies,with the charging electrode functioning as the anode and the terminalelectrode body functioning as the cathode, such that the reducible metalfuel ions are reduced and electrodeposited as metal fuel in oxidizableform on the terminal permeable electrode body, said electrodepositioncausing growth of the metal fuel among the permeable electrode bodiessuch that the electrodeposited metal fuel establishes an electricalconnection between the terminal electrode body and each subsequentpermeable electrode body with said reduction and deposition occurring oneach subsequent permeable electrode body upon establishment of saidelectrical connection; and wherein, in the higher rate growth mode, saidcharging comprises: applying the electrical current simultaneously to aplurality of said electrode bodies, with the charging electrodefunctioning as the anode and each of the plurality of electrode bodiesfunctioning as cathodes, such that the reducible metal fuel ions arereduced and electrodeposited as metal fuel in oxidizable form on theterminal permeable electrode body, said electrodeposition causing growthof the metal fuel among the permeable electrode bodies; anddisconnecting the electrical current to discontinue the charging.
 19. Amethod of recharging the electrochemical cell according to claim 18,wherein, in the higher rate growth mode, the charging electrodecomprises one or more of the plurality of electrode bodies adjacent tothe plurality of the electrode bodies functioning as cathodes
 20. Amethod of recharging the electrochemical cell according to claim 18,wherein, in the higher rate growth mode, said charging further comprisesperforming continuity testing on one or more of the plurality ofelectrode bodies to determine electrical connections formed between anyof the electrode bodies functioning as cathodes and any of the chargingelectrode; and disconnecting any of the electrode bodies.
 21. A methodof recharging the electrochemical cell according to claim 18, whereinthe at least one input parameter comprises measurements obtained by asensor associated with the electrochemical cell, and wherein the methodfurther comprises sensing, with the sensor, the measurements of theelectrochemical cell.
 22. A method of recharging the electrochemicalcell according to claim 18, wherein the at least one input parametercomprises a user selection of the higher density progressive charge modeor the higher rate growth mode, input via a user input, wherein themethod further comprises receiving a user selection via the user input.23. A method of recharging the electrochemical cell according to claim18, wherein the at least one input parameter is a limit parameter andwherein the controller is further configured to compare a cell propertyto the limit parameter to perform said selecting.
 24. A method ofrecharging the electrochemical cell according to claim 18, wherein, inthe higher rate growth mode, said charging comprises applying theelectrical current simultaneously to all of the electrode bodies.
 25. Amethod of recharging the electrochemical cell according to claim 18,wherein, in the higher rate growth mode, said charging comprisesapplying the electrical current simultaneously to less than all of theelectrode bodies.
 26. A method of recharging the electrochemical cellaccording to claim 18, wherein said charging comprises varying, with thecontroller, the number of electrode bodies to which the electricalcurrent is applied while performing a recharging operation.
 27. A methodof recharging the electrochemical cell according to claim 18, whereinthe ionically conductive medium of the electrochemical cell is anelectrolyte.
 28. A method of recharging the electrochemical cellaccording to claim 18, wherein the electrochemical cell furthercomprises a plurality of switches operatively coupled between thecontroller and the plurality of electrode bodies, and wherein saidcharging comprises controlling an open state and a closed state for eachof the plurality of switches with the controller, to selectively applythe electrical current to some of the plurality of electrode bodies. 29.A method of recharging the electrochemical cell according to claim 18,wherein in the higher rate growth mode, said charging comprises applyingthe electrical current simultaneously to the plurality of electrodebodies such that the charging electrode comprises some of the pluralityof electrode bodies functioning as anodes and the fuel electrodecomprises some of the plurality of electrode bodies functioning ascathodes, and wherein each of the plurality of electrode bodiesfunctioning as cathodes are separated from one another by the pluralityof electrode bodies functioning as anodes.
 30. A method according toclaim 18, wherein the controller is a charge/discharge controller.
 31. Amethod according to claim 21, wherein the controller is acharge/discharge controller.
 32. A method according to claim 23, whereinthe controller is a charge/discharge controller.
 33. A method accordingto claim 28, wherein the controller is a charge/discharge controller.